1. Field of the Invention
This invention relates to the field of drainage systems for athletic fields, particularly for natural grass fields.
2. Statement of the Problem
The drainage of athletic playing fields has been a longstanding problem. The earliest athletic fields were level-graded, natural grass fields. These fields tended to have poor drainage, causing water to collect on the surface and subsurface. Activity on the fields under these conditions tended to cause damage to the fields as well as hinder the activity on the fields. Providing the fields with a crowned surface to enhance the drainage did little to alleviate the problem.
Artificial surface athletic fields were developed partially to solve this problem. However, artificial surface playing fields are expensive to install and maintain, retain heat on the surface of the field, and most importantly, increases the risk of injury to persons partaking in activity on the artificial surface fields. Artificial surface fields also require crowned surfaces for surface drainage which can create problems with depth perception and with other injuries.
Several approaches have attempted to solve the problems associated with natural grass fields and artificial surface fields by the use of subdrainage. These approaches are relatively expensive and cumbersome.
One such approach is disclosed in U.S. Pat. No. 3,908,385 for a planted surface conditioning system. This system uses a watertight barrier placed over the compacted subsoil beneath the playing field. A series of slitted drain pipes are laid over the barrier under the playing field. A layer of porous sand is then placed over the drain pipes with a mixture layer of different soils placed over the sand to form a rooting medium for the grass. A vacuum pump is utilized to pump the water from the playing field to prevent accumulations of water on the surface or subsurface.
U.S. Pat. No. 4,268,993 discloses a natural grass surface subdrainage system using a watertight membrane placed over a sloping-graded subgrade. A layer of gravel is placed over the membrane with a series of slitted drain pipes placed over the gravel on a level horizontal grade to maintain a water table in the gravel layer. A layer of sand is placed over the drain pipes and gravel layer to anchor the grass. A series of valves and water sensor stations monitor and maintain the water table beneath the surface. The system is primarily used to subirrigate the field.
U.S. Pat. No. 4,913,596 discloses a natural grass athletic field construction using a sloped subgrade having lateral trenches formed therein. Slitted drain pipes are laid into the trenches with a layer of gravel laid over the pipes, a layer of crushed stone laid over the gravel layer, a layer of sand laid over the crushed stone layer, and a layer of soil mixture laid over the crushed stone layer with grass on the soil mixture layer. A plastic reinforcement matting is spaced from the upper surface two inches into the soil mixture. Each individual layer of sand, gravel and stone has an infiltration level of at least 9 inches per hour, with the soil layer having an infiltration rate of 5 to 9 inches per hour. The upper surface is crowned to enhance the drainage of the field.
The above described systems are typical of the approaches for providing subdrainage for natural grass athletic fields. These systems require expensive construction methods and materials. Also, the use of watertight membranes increase the cost of installation 20 and maintenance as well as providing additional opportunities for problems to arise. The cost of the systems are above the ability of all but professional sports teams or athletic departments having large budgets to afford to install and maintain. These approaches also fail to consider the problems of rootzone drainage and of the layering effects of the subsoil mixtures.
A need exists for a drainage system for natural turf athletic fields that is economical to install and maintain, that is effective to drain high rates of rain or irrigation, and that will decrease the probability of injury.
3. Solution to the Problem
The present invention solves these and other problems by providing a gravity drainage system for natural turf athletic fields.
The present invention provides a subdrainage system using gravity to drain the subsurface of the athletic field.
The present invention provides a system that is relatively inexpensive to install and requires little mechanical maintenance after installation.
The present invention provides a system that provides adequate drainage after the rootzone of the grass surface is established.
The present invention provides a system that is easily adaptable to fit the needs of a specific site.
The present invention provides a system that is easy to clean and maintain.
These and other features of the present invention will become evident from the following description taken in conjunction with the drawings.